Stretching rolls



Dec. 24, 1946. A. M. SAW 2,413,073"

STRETCHING ROLLS Filed July 26, 1945 INVEN TOR.

Aytlzar jlf L amz. "zfl/Zk! A T TORNE Y Patented Dec. 24, 1946 UNITED \STATESQPATENT. OFFICE STRETCHING ROLLS Arthur M. Saum, Wilmington, Dei., assignor to E. I. du Pont de Nemours & Company, Wilmlngton, Del., a corporation of Delaware Application J nly 26, 1945, Serial No. 607,234

4 Claims. 1 n

This invention relates to the manufacture of artificial filaments, yarns, threads, ribbons, etc., and more particularly to an improved arrangement to prevent slippage of artificial filaments, yarns, threads, ribbons and the like under ten-' sion on positively driven advancing rolls.

Heretofore, much diiiiculty has been experienced in the stretching or drawing of yarns and the like by means of two or more sets of positively driven rolls turning at different peripheral speeds due to inconstant slippage of the yarn thereon. Various arrangements have been proposed and used, such asa plurality of turns of the yarn about th advancing roll and about a suitable auxiliary roller for displacing the yarn in its several passes about the advancing roll, pressure rolls bearing on the yarn passing around the yarn advancing roll, etc. These prior arrangements work quite satisfactorily when the tension diiierential between the oncoming and ofigoing yarn is not too great. However, where the tension difierences are large, yarn slippage on the advanclng roll occurs and the stretching ratio becomes variable. This culty is especially acute in the drawing of heavy denier yarns or filaments of nylon which require an unusually large force to attenuate the structure to approximately four times its original length.

It is, therefore, an object of this invention to provide an improved yarn advancing roll arrangement that is simple to make and install, easily strung up, and, in operation, capable or preventing slippage oi the yarn on the advancing roll even though the tensions on the yarn thereto and therefrom difier widely. Other objects will be apparent from the description that follows which is to be read in connection with the accompanying drawing wherein:

Figure l is a diagrammatic illustration of one arrangement of yarn advancing rolls embog the principles of my invention;

Figure 2 is a diagrammatic representation of an alternate arrangement of rolls according to my invention; and

Figure 3 illustrates a med form of the pinch roll.

These objects are accomplished by my invenlation with the feed roll in a manner .hereinaiter fully described, whereby yarn passed over and. between the feed and pinch rolls will cause the pinch roll to be iorced against the teed roll and pinch the yarn therebetween with a force sumcient to prevent slippage oi the yarn on the feed roll.

Referring now to the drawing wherein like reference numerals designate like parts. reference numeral i (Fig. 1) indicates a freely rotatable pinch roll l, aligned parallel to the usual positively driven feed roll 2, and mounted for swing on one end of a swing arm 3 which is pivoted at the opposite end to the frame of the spinning machine or any other suitable support. The swing arm and attached pinch roll may be disposed at any point about the feed roll so long as the pull on the yarn passing over and between the rolls will tend to done the rolls into contact, and the length of the swing arm and the radius of the pinch roll are such that the pinch roll cannot be swung past the feed roll. It is further required that'the pivot point of the-swing arm be so located that the obtuse angle a formed by the intersection of the straight line passing through and connecting the centers of the two rolls andthe straight line passing through and connecting the center of the pinch roll and pivot point of the swing arm is within the range of from 165 to just short of 180". In the arrangement shown in Fig. i, the distance between the axes of rotation of the swing arm 3 and of the feed roll 2 is slightly less than the sum of the length'of the swing arm (distance between the axis of rotaticnof the swing arm and axis of rotation of roll 3) and the radii of the pinch roll i and the feed roll 2. in order that the pinch roll cannot quite swing past the feed roll. Moreover, the center points oi the two rolls and the pivot point or theswing arm are almost in a straight line, i. e., the angle a is almost 180". With this arrangement a force which tends to push the pinch roll pat the feed roll develops a much greater compressive force between the two roll surfaces than can be obtained if the pinch roll is supported in vertical guideways directly for the stretching of artificial yarn and the like,

a freely rotatable, swinghbly mounted roll (hereinafter termed fpinch roll") having its axis of rotation parallel to the axis of rotation of the mil, and further disposed in contacting reover the feed roll or ifthe swing of a swing ably mounted pinch roll is so pivoted that the angle or isless, than about When the yarn strung around the rolls disposed in accordance with the principles of this invention and in such a way that the tension on the yarn as it is withdrawn tends to pull the pinch roll past the iced roll, then the pinching action between the rolls grips the yarn more firmly as the yarn tension to cause the pinch roll to be forced against the 1 advancing roll, and the surfaces of the two rolls should in part at least be such that the coefiicient of friction between them is relatively high. Preferably the feed roll is a steel-surfaced roll while the pinch roll is rubber-, corkor leathercovered.v While the feed roll could be covered with rubber, or leather, or cork, and the pinch roll steel-surfaced, a frictional loss will occur reducing the resistance to slipp e of the yarn on these rolls since the relatively large arc of contact of the yarn with the pinch roll under high tension becomes less effective than if the two rolls were surfaced as first described. A satisfactory pinch action between steel-surfaced rolls can be obtained by providing one of the rolls with end bands 4 or i as shown in Fig. 3. These bands are of a diameter slightly larger than that of the roll and are constructed of rubber or like resilient material having a high coefilcient of friction.

The feed roll assembly above described is especially useful in feeding large denier undrawn nylon yarn or a large denier undrawn nylon filament to another pair of rolls turning at substantially higher peripheral speed to stretch the yarn or filaments approximately four times their original length. As disclosed in U. 8. Patent No. 2,289,232 to D. 1"..Babcock, a draw Din is preferably positioned between two sets of rolls. Even though the force required to stretch the yarn or filament to four times its length is as much as as 1000 denier or more, and large diameter nylon filaments such as may be used for bristles, horse hair substitutes. tennis racket strings, musical instrument strings, fish line leaders, surgical sutures, screening, etc., and ranging in size from 0.002 to 0.06 inch in diameter, the invention may also be used in connection with the feeding .or advancing of yarn tow, or filaments of any character where a; very high tension differential exists in the yarn in going on and coming 01! the advancing roll arrangement. This invention-is uset 4 ful, too, to improve twist uniformity in difiicultly handled structures such as tire cord.

By means of this invention, heavy denier yarns and filaments of nylon have been produced with more uniform physical properties than has been possible heretofore, by virtue of the elimination of yarn or filament slippage on the draw rolls.

Furthermore, the arrangement described can be very quickly strung up" and is easily restrung whenever a break occurs.

As many apparently different embodiments c this invention can be made without departing from the spirit and scope thereof, it is to be understood that said invention is not to be restricted save as defined by the appended claims.

I claim:

1. In combination, a driven roll positively driven about a fixed axis, a pinch roll in contact with said driven roll and freely rotatable on an axis parallel to the fixedaxis of the driven roll, said pinch roll being mounted on the free end of a swing arm which is pivoted at the opposite end, the pivot point of said swing arm being fixed and so located that the obtuse angle formed by the straight line connecting the centers of the two rolls in operative contacting position and the straight line connecting the center of the pinch roll and the pivot p int of said arm is within the range of from 165 to Just short of 180.

2. In apparatus for stretching stretchable material wherein the material is stretched between positively driven rolls, the improvement which comprises in combination with the first of said driven rolls positively driven about a fixed axis.

a swing arm pivoted at one end. a pinch roll mounted on the free end of said arm and freely rotatable about an axis parallel to said fixed axis, said pinch roll being further positioned so that it swings on said arm into contact with.

said first driven roll, and the pivot point of said arm being fixed and so located that the obtuse angle formed by the intersection of a straight line passing through and connecting the axes of the first driven roll and the pinch roll in operative 'contacting position and a straight line passing through and connecting the axis of the pinch roll and the pivot point of the arm is within the range of from to Just short of whereby material passing between the first driven and pinch rolls and drawn ofi the pinch roll under tension in a direction effective to urge the pinch roll into contact with the first driven roll is subjected to a pinch pressure sufficient to prevent slippa e of said material on said first driven roll. v

3. Apparatus according to claim 2 wherein either one of the two contacting rolls is surfaced with a material having a coefilcient of friction which is high relative to the ccefilcient of friction of the surface of the other roll.

4. Apparatus according to claim 1 wherein the first driven roll is steel-surfaced and the pinch roll is surfaced with a material having a substantially higher coefficient of friction.

ARTHUR M. SAUM. 

